On 25 December 800, Pope Leo III crowned the Frankish kingCharlemagne as Emperor, reviving the title in Western Europe after more than three centuries. The title continued in the Carolingian family until 888, after which it was contested by the rulers of Italy in a series of civil wars until the death of the last Italian claimant, Berengar, in 924. The title was revived in 962 when Otto I was crowned emperor, fashioning himself as the successor of Charlemagne[10] and beginning a continuous existence of the empire for over eight centuries.[11][12][13] Some historians refer to the coronation of Charlemagne as the origin of the empire,[14][15] while others prefer the coronation of Otto I as its beginning.[16][17] Scholars generally concur, however, in relating an evolution of the institutions and principles constituting the empire, describing a gradual assumption of the imperial title and role.[8][14]

The precise term Holy Roman Empire was not used until the 13th century, but the concept of translatio imperii[e] was fundamental to the prestige of the emperor, the notion that he held supreme power inherited from the emperors of Rome.[8] The office of Holy Roman Emperor was traditionally elective, although frequently controlled by dynasties. The German prince-electors, the highest ranking noblemen of the empire, usually elected one of their peers as "King of the Romans", and he would later be crowned emperor by the Pope; the tradition of papal coronations was discontinued in the 16th century. The empire never achieved the extent of political unification formed in France, evolving instead into a decentralized, limited elective monarchy composed of hundreds of sub-units, principalities, duchies, counties, Free Imperial Cities, and other domains.[9][18] The power of the emperor was limited, and while the various princes, lords, and kings of the empire were vassals and subjects who owed the emperor their allegiance, they also possessed an extent of privileges that gave them de facto sovereignty within their territories. Emperor Francis II dissolved the empire on 6 August 1806, after its defeat by Napoleon at the Battle of Austerlitz.

In various languages the Holy Roman Empire was known as: Latin: Sacrum Imperium Romanum, German: Heiliges Römisches Reich, Italian: Sacro Romano Impero, Czech: Svatá říše římská, Slovene: Sveto rimsko cesarstvo, Dutch: Heilige Roomse Rijk, French: Saint-Empire romain germanique.[19] Before 1157, the realm was merely referred to as the Roman Empire.[20] The term sacrum ("holy," in the sense of "consecrated") in connection with the medieval Roman Empire was used beginning in 1157, under Frederick I Barbarossa ("Holy Empire") – the term was added to reflect Frederick's ambition to dominate Italy and the Papacy;[21] the form "Holy Roman Empire" is attested from 1254 onward.[22]

In a decree following the 1512 Diet of Cologne, the name was officially changed to Holy Roman Empire of the German Nation (German: Heiliges Römisches Reich Deutscher Nation, Latin: Imperium Romanum Sacrum Nationis Germanicæ),[23][24] a form first used in a document in 1474.[21] The new title was adopted partly because the Empire had lost most of its Italian and Burgundian (Kingdom of Arles) territories by the late 15th century,[25] but also to emphasize the new importance of the German Imperial Estates in ruling the Empire due to the Imperial Reform.[26] However, by the end of the 18th century, the term 'Holy Roman Empire of the German Nation' had fallen out of official use. As Hermann Weisert points out, "Documents were thirty times as likely to omit this 'national' suffix as include it." [27]

In a famous assessment of the name, the French Enlightenment writer Voltaire remarked sardonically: "This agglomeration which was called and which still calls itself the Holy Roman Empire was neither holy, nor Roman, nor an empire."[28]

Henry died in 936, but his descendants, the Liudolfing (or Ottonian) dynasty, would continue to rule the Eastern kingdom for roughly a century. Upon Henry the Fowler's death Henry's designated successor, Otto, Henry's own son,[33] was elected King in Aachen in 936.[34]:706 He overcame a series of revolts from an elder brother and from several dukes. After that, the king managed to control the appointment of dukes and often also employed bishops in administrative affairs.[35]:212–13

The Kingdom had no permanent capital city.[36] Kings traveled between residences (called Kaiserpfalz) to discharge affairs. However, each king preferred certain places; in Otto's case, this was the city of Magdeburg. Kingship continued to be transferred by election, but Kings often had their sons elected during their lifetime, enabling them to keep the crown for their families. This only changed after the end of the Salian dynasty in the 12th century.

In 955, Otto won a decisive victory over the Magyars in the Battle of Lechfeld.[34]:707 In 951, Otto came to the aid of Adelaide, the widowed queen of Italy, defeating her enemies, marrying her, and taking control over Italy.[35]:214–15 In 962, Otto was crowned Emperor by Pope John XII,[34]:707 thus intertwining the affairs of the German kingdom with those of Italy and the Papacy. Otto's coronation as Emperor marked the German kings as successors to the Empire of Charlemagne, which through the concept of translatio imperii, also made them consider themselves as successors to Ancient Rome. Additionally, in 963, Otto deposed the current pope John XII and chose Pope Leo VIII as the new pope (although John XII and Leo VIII both claimed the papacy until 964, when John XII died).

The Holy Roman Empire in 1400

This also renewed the conflict with the Eastern Emperor in Constantinople, especially after Otto's son Otto II (r. 967–83) adopted the designation imperator Romanorum. Still, Otto formed marital ties with the east when he married the Byzantine princess Theophanu.[34]:708

Their son, Otto III, came to the throne only three years old, and was subjected to a power struggle and series of regencies until his age of majority in 994. Up to that time, he had remained in Germany, while a deposed Duke, Crescentius II, ruled over Rome and part of Italy, ostensibly in his stead.

Kings often employed bishops in administrative affairs and often determined who would be appointed to ecclesiastical offices.[39]:101–134 In the wake of the Cluniac Reforms, this involvement was increasingly seen as inappropriate by the Papacy. The reform-minded Pope Gregory VII was determined to oppose such practices, leading to the Investiture Controversy with King Henry IV (r. 1056–1106),[39]:101–134 who repudiated the Pope's interference and persuaded his bishops to excommunicate the Pope, whom he famously addressed by his born name "Hildebrand", rather than his regnal name "Pope Gregory VII".[39]:109 The Pope, in turn, excommunicated the king, declared him deposed, and dissolved the oaths of loyalty made to Henry.[11][39]:109 The king found himself with almost no political support and was forced to make the famous Walk to Canossa in 1077,[39]:122–24 by which he achieved a lifting of the excommunication at the price of humiliation. Meanwhile, the German princes had elected another king, Rudolf of Swabia.[39]:123 Henry managed to defeat him but was subsequently confronted with more uprisings, renewed excommunication, and even the rebellion of his sons. It was his second son, Henry V, who managed to reach an agreement with both the Pope and the bishops in the 1122 Concordat of Worms.[39]:123–34 The political power of the Empire was maintained, but the conflict had demonstrated the limits of any ruler's power, especially in regard to the Church, and it robbed the king of the sacral status he had previously enjoyed. Both the Pope and the German princes had surfaced as major players in the political system of the Empire.

When the Salian dynasty ended with Henry V's death in 1125, the princes chose not to elect the next of kin, but rather Lothair, the moderately powerful but already old Duke of Saxony. When he died in 1137, the princes again aimed at checking royal power; accordingly they did not elect Lothair's favoured heir, his son-in-law Henry the Proud of the Welf family, but rather Conrad III of the Hohenstaufen family, the grandson of Emperor Henry IV and thus a nephew of Emperor Henry V. This led to over a century of strife between the two houses. Conrad ousted the Welfs from their possessions, but after his death in 1152, his nephew Frederick I "Barbarossa" succeeded him and made peace with the Welfs, restoring his cousin Henry the Lion to his — albeit diminished — possessions.

The Hohenstaufen rulers increasingly lent land to ministerialia, formerly non-free service men, whom Frederick hoped would be more reliable than dukes. Initially used mainly for war services, this new class of people would form the basis for the later knights, another basis of imperial power. A further important constitutional move at Roncaglia was the establishment of a new peace mechanism for the entire Empire, the Landfrieden, which attempted to abolish private feuds, between the many dukes and beyond, and to tie the Emperor's subordinates to a legal system of jurisdiction and public prosecution of criminal acts — a predecessor of the modern concept of "rule of law." Another new concept of the time was the systematic foundation of new cities, both by the Emperor and the local dukes. These were partly caused by the explosion in population, but they also concentrated economic power at strategic locations, while formerly cities had only existed in the form of old Roman foundations or older bishoprics. Cities that were founded in the 12th century include Freiburg, possibly the economic model for many later cities, and Munich.

Frederick I, also called Frederick Barbarossa, was crowned Emperor in 1155. He emphasized the "Romanness" of the Empire, partly in an attempt to justify the power of the Emperor independent of the (now strengthened) Pope. An imperial assembly at the fields of Roncaglia in 1158 reclaimed imperial rights in reference to Justinian's Corpus Juris Civilis. Imperial rights had been referred to as regalia since the Investiture Controversy, but were enumerated for the first time at Roncaglia as well. This comprehensive list included public roads, tariffs, coining, collecting punitive fees, and the investiture, the seating and unseating of office holders. These rights were now explicitly rooted in Roman Law, a far-reaching constitutional act.

Frederick's policies were primarily directed at Italy, where he clashed with the increasingly wealthy and free-minded cities of the north, especially Milan. He also embroiled himself in another conflict with the Papacy by supporting a candidate elected by a minority against Pope Alexander III (1159–81). Frederick supported a succession of antipopes before finally making peace with Alexander in 1177. In Germany, the Emperor had repeatedly protected Henry the Lion against complaints by rival princes or cities (especially in the cases of Munich and Lübeck). Henry gave only lackluster support to Frederick's policies, and in a critical situation during the Italian wars, Henry refused the Emperor's plea for military support. After returning to Germany, an embittered Frederick opened proceedings against the Duke, resulting in a public ban and the confiscation of all his territories. In 1190, Frederick participated in the Third Crusade and died in Asia Minor.

Under the son and successor of Frederick Barbarossa, Henry VI, the Hohenstaufen dynasty reached its apex. Henry added the Norman kingdom of Sicily to his domains, held English king Richard the Lionheart captive, and aimed to establish a hereditary monarchy when he died in 1197. As his son, Frederick II, though already elected king, was still a small child and living in Sicily, German princes chose to elect an adult king, resulting in the dual election of Frederick Barbarossa's youngest son Philip of Swabia and Henry the Lion's son Otto of Brunswick, who competed for the crown. Otto prevailed for a while, after Philip was murdered in a private squabble in 1208, until he began to also claim Sicily.

Pope Innocent III, who feared the threat posed by a union of the Empire and Sicily, now supported Frederick II, who marched to Germany and defeated Otto. After his victory, Frederick did not act upon his promise to keep the two realms separate – though he had made his son Henry king of Sicily before marching on Germany, he still reserved real political power for himself. This continued after Frederick was crowned Emperor in 1220. Fearing Frederick's concentration of power, the Pope finally excommunicated the Emperor. Another point of contention was the crusade, which Frederick had promised but repeatedly postponed. Now, though excommunicated, Frederick led the Sixth Crusade in 1228, which ended in negotiations and a temporary restoration of the Kingdom of Jerusalem.

Despite his imperial claims, Frederick's rule was a major turning point towards the disintegration of central rule in the Empire. While concentrated on establishing a modern, centralized state in Sicily, he was mostly absent from Germany and issued far-reaching privileges to Germany's secular and ecclesiastical princes: In the 1220 Confoederatio cum principibus ecclesiasticis, Frederick gave up a number of regalia in favour of the bishops, among them tariffs, coining, and fortification. The 1232 Statutum in favorem principum mostly extended these privileges to secular territories. Although many of these privileges had existed earlier, they were now granted globally, and once and for all, to allow the German princes to maintain order north of the Alps while Frederick concentrated on Italy. The 1232 document marked the first time that the German dukes were called domini terræ, owners of their lands, a remarkable change in terminology as well.

The Kingdom of Bohemia was a significant regional power during the Middle Ages. In 1212, King Přemysl Otakar I (bearing the title "king" since 1198) extracted a Golden Bull of Sicily (a formal edict) from the emperor Frederick II, confirming the royal title for Otakar and his descendants and the Duchy of Bohemia was raised to a kingdom. Czech kings should be exempt from all future obligations to the Holy Roman Empire except for participation in the imperial councils. Charles IV set Prague to be the seat of the Holy Roman Emperor and thus it also became the capital of the Holy Roman Empire.

After the death of Frederick II in 1250, the German kingdom was divided between his son Conrad IV (died 1254) and the anti-king, William of Holland (died 1256). Conrad's death was followed by the Interregnum, during which no king could achieve universal recognition, allowing the princes to consolidate their holdings and become even more independent rulers. After 1257, the crown was contested between Richard of Cornwall, who was supported by the Guelph party, and Alfonso X of Castile, who was recognized by the Hohenstaufen party but never set foot on German soil. After Richard's death in 1273, the Interregnum ended with the unanimous election of Rudolf I of Germany, a minor pro-Staufen count.

An illustration from Schedelsche Weltchronik depicting the structure of the Reich: The Holy Roman Emperor is sitting; on his left are three ecclesiastics; on his right are four secular electors.

During the 13th century, a general structural change in how land was administered prepared the shift of political power towards the rising bourgeoisie at the expense of aristocratic feudalism that would characterize the Late Middle Ages. Instead of personal duties, money increasingly became the common means to represent economic value in agriculture. Peasants were increasingly required to pay tribute for their lands. The concept of "property" began to replace more ancient forms of jurisdiction, although they were still very much tied together. In the territories (not at the level of the Empire), power became increasingly bundled: Whoever owned the land had jurisdiction, from which other powers derived. It is important to note, however, that jurisdiction at this time did not include legislation, which virtually did not exist until well into the 15th century. Court practice heavily relied on traditional customs or rules described as customary.

During this time territories began to transform into the predecessors of modern states. The process varied greatly among the various lands and was most advanced in those territories that were most identical to the lands of the old Germanic tribes, e.g. Bavaria. It was slower in those scattered territories that were founded through imperial privileges.

The difficulties in electing the king eventually led to the emergence of a fixed college of Prince-electors (Kurfürsten), whose composition and procedures were set forth in the Golden Bull of 1356, which was valid until 1806. This development probably best symbolizes the emerging duality between emperor and realm (Kaiser und Reich), which were no longer considered identical. The Golden Bull also set the election system of the Holy Roman Emperor. The emperor now had to be elected by a majority rather than by consent of all seven electors. For electors the title became hereditary, and they were given the right to mint coins and to exercise jurisdiction. Also their sons were to know the imperial languages – German, Italian, and Czech.[40][verification needed]

The shift in power away from the emperor is also revealed in the way the post-Hohenstaufen kings attempted to sustain their power. Earlier, the Empire's strength (and finances) greatly relied on the Empire's own lands, the so-called Reichsgut, which always belonged to the king of the day and included many Imperial Cities. After the 13th century, the relevance of the Reichsgut faded, even though some parts of it did remain until the Empire's end in 1806. Instead, the Reichsgut was increasingly pawned to local dukes, sometimes to raise money for the Empire, but more frequently to reward faithful duty or as an attempt to establish control over the dukes. The direct governance of the Reichsgut no longer matched the needs of either the king or the dukes.

The kings beginning with Rudolf I of Germany increasingly relied on the lands of their respective dynasties to support their power. In contrast with the Reichsgut, which was mostly scattered and difficult to administer, these territories were relatively compact and thus easier to control. In 1282, Rudolf I thus lent Austria and Styria to his own sons. In 1312, Henry VII of the House of Luxembourg was crowned as the first Holy Roman Emperor since Frederick II. After him all kings and emperors relied on the lands of their own family (Hausmacht): Louis IV of Wittelsbach (king 1314, emperor 1328–47) relied on his lands in Bavaria; Charles IV of Luxembourg, the grandson of Henry VII, drew strength from his own lands in Bohemia. Interestingly, it was thus increasingly in the king's own interest to strengthen the power of the territories, since the king profited from such a benefit in his own lands as well.

The "constitution" of the Empire was still largely unsettled at the beginning of the 15th century. Although some procedures and institutions had been fixed, for example by the Golden Bull of 1356, the rules of how the king, the electors, and the other dukes should cooperate in the Empire much depended on the personality of the respective king. It therefore proved somewhat damaging that Sigismund of Luxemburg (king 1410, emperor 1433–37) and Frederick III of Habsburg (king 1440, emperor 1452–93) neglected the old core lands of the empire and mostly resided in their own lands. Without the presence of the king, the old institution of the Hoftag, the assembly of the realm's leading men, deteriorated. The Imperial Diet as a legislative organ of the Empire did not exist at that time. Even worse, dukes often went into feuds against each other that, more often than not, escalated into local wars.

Map of the Empire showing division into Circles in 1512

Simultaneously, the Church was in a state of crisis too, with wide-reaching effects in the Empire. The conflict between several papal claimants (two anti-popes and the legitimate Pope) was only resolved at the Council of Constance (1414–18); after 1419, much energy was spent on fighting the Hussites. The medieval idea of unifying all Christendom into a single political entity, of which the Church and the Empire were the leading institutions, began to decline.

With these drastic changes, much discussion emerged in the 15th century about the Empire itself. Rules from the past no longer adequately described the structure of the time, and a reinforcement of earlier Landfrieden was urgently called for. During this time, the concept of "reform" emerged, in the original sense of the Latin verb re-formare, to regain an earlier shape that had been lost.

When Frederick III needed the dukes to finance war against Hungary in 1486 and at the same time had his son, later Maximilian I elected king, he was presented with the dukes' united demand to participate in an Imperial Court. For the first time, the assembly of the electors and other dukes was now called the Imperial Diet (German Reichstag) (to be joined by the Imperial Free Cities later). While Frederick refused, his more conciliatory son finally convened the Diet at Worms in 1495, after his father's death in 1493. Here, the king and the dukes agreed on four bills, commonly referred to as the Reichsreform (Imperial Reform): a set of legal acts to give the disintegrating Empire back some structure. Among others, this act produced the Imperial Circle Estates and the Reichskammergericht (Imperial Chamber Court); structures that would—to a degree—persist until the end of the Empire in 1806.

However, it took a few more decades until the new regulation was universally accepted and the new court actually began to function; only in 1512 would the Imperial Circles be finalized. The King also made sure that his own court, the Reichshofrat, continued to function in parallel to the Reichskammergericht. In this year, the Empire also received its new title, the Heiliges Römisches Reich Deutscher Nation ("Holy Roman Empire of the German Nation").

In 1516, Ferdinand II of Aragon, grandfather of the future Holy Roman Emperor Charles V, died. Due to a combination of (1) the traditions of dynastic succession in Aragon, which permitted maternal inheritance with no precedence for female rule; (2) the insanity of Charles's mother, Joanna of Castile; and (3) the insistence by his remaining grandfather, Maximilian I, that he take up his royal titles, Charles initiated his reign in Castile and Aragon, a union which evolved into Spain, in conjunction with his mother. This ensured for the first time that all the realms of the Iberian peninsula (save for Portugal) would be united by one monarch under one nascent Spanish crown, with the founding territories retaining their separate governance codes and laws. In 1519, already reigning as Carlos I in Spain, Charles took up the imperial title as Karl V. The balance (and imbalance) between these separate inheritances would be defining elements of his reign, and would ensure that personal union between the Spanish and German crowns would be short-lived. The latter would end up going to a more junior branch of the Habsburgs in the person of Charles's brother Ferdinand, while the senior branch continued rule in Spain and in the Burgundian inheritance in the person of Charles's son, Philip II of Spain.

In addition to conflicts between his Spanish and German inheritances, conflicts of religion would be another source of tension during the reign of Charles V. Before Charles even began his reign in the Holy Roman Empire, in 1517, Martin Luther initiated what would later be known as the Reformation. At this time, many local dukes saw it as a chance to oppose the hegemony of Emperor Charles V. The empire then became fatally divided along religious lines, with the north, the east, and many of the major cities—Strasbourg, Frankfurt and Nuremberg—becoming Protestant while the southern and western regions largely remained Catholic.

Charles V continued to battle the French and the Protestant princes in Germany for much of his reign. After his son Philip married Queen Mary of England, it appeared that France would be completely surrounded by Habsburg domains, but this hope proved unfounded when the marriage produced no children. In 1555, Paul IV was elected pope and took the side of France, whereupon an exhausted Charles finally gave up his hopes of a world Christian empire. He abdicated and divided his territories between Philip and Ferdinand of Austria. The Peace of Augsburg ended the war in Germany and accepted the existence of the Protestant princes, although not Calvinism, Anabaptism, or Zwingliism.

Germany would enjoy relative peace for the next six decades. On the eastern front, the Turks continued to loom large as a threat, although war would mean further compromises with the Protestant princes, and so the Emperor sought to avoid it. In the west, the Rhineland increasingly fell under French influence. After the Dutch revolt against Spain erupted, the Empire remained neutral; de facto allowing the Netherlands to depart the empire in 1581, a succession acknowledged in 1648. A side effect was the Cologne War, which ravaged much of the upper Rhine.

After Ferdinand died in 1564, his son Maximilian II became Emperor, and like his father, accepted the existence of Protestantism and the need for occasional compromise with it. Maximilian was succeeded in 1576 by Rudolf II, a strange man who preferred classical Greek philosophy to Christianity and lived an isolated existence in Bohemia. He became afraid to act when the Catholic Church was forcibly reasserting control in Austria and Hungary and the Protestant princes became upset over this. Imperial power sharply deteriorated by the time of Rudolf's death in 1612. When Bohemians rebelled against the Emperor, the immediate result was the series of conflicts known as the Thirty Years' War (1618–48), which devastated the Empire. Foreign powers, including France and Sweden, intervened in the conflict and strengthened those fighting Imperial power, but also seized considerable territory for themselves. The long conflict so bled the Empire that it never recovered its strength.

At the Battle of Vienna (1683), the Army of the Holy Roman Empire, led by the Polish King John III Sobieski, decisively defeated a large Turkish army, ending the western colonial Ottoman advance and leading to the eventual dismemberment of the Ottoman Empire in Europe. The HRE army was half Polish/Lithuanian Commonwealth forces, mostly cavalry, and half Holy Roman Empire forces (German/Austrian), mostly infantry.

The Holy Roman Empire was not a highly centralized state like most countries today. Instead, it was divided into dozens—eventually hundreds—of individual entities governed by kings,[41]dukes, counts, bishops, abbots and other rulers, collectively known as princes. There were also some areas ruled directly by the Emperor. At no time could the Emperor simply issue decrees and govern autonomously over the Empire. His power was severely restricted by the various local leaders.

From the High Middle Ages onwards, the Holy Roman Empire was marked by an uneasy coexistence of the princes of the local territories who were struggling to take power away from it. To a greater extent than in other medieval kingdoms such as France and England, the Emperors were unable to gain much control over the lands that they formally owned. Instead, to secure their own position from the threat of being deposed, Emperors were forced to grant more and more autonomy to local rulers, both nobles and bishops. This process began in the 11th century with the Investiture Controversy and was more or less concluded with the 1648 Peace of Westphalia. Several Emperors attempted to reverse this steady dissemination of their authority, but were thwarted both by the papacy and by the princes of the Empire.

The number of territories in the Empire was considerable, rising to approximately 300 at the time of the Peace of Westphalia. Many of these Kleinstaaten ("little states") covered no more than a few square miles, or included several non-contiguous pieces, so the Empire was often called a Flickenteppich ("patchwork carpet").

An entity was considered a Reichsstand (imperial estate) if, according to feudal law, it had no authority above it except the Holy Roman Emperor himself. The imperial estates comprised:

Territories ruled by a hereditary nobleman, such as a prince, archduke, duke, or count.

Territories in which secular authority was held by a clerical dignitary, such as an archbishop, bishop, or abbot. Such a cleric was a prince of the church. In the common case of a prince-bishop, this temporal territory (called a prince-bishopric) frequently overlapped with his often-larger ecclesiastical diocese, giving the bishop both civil and clerical powers. Examples include the three prince-archbishoprics: Cologne, Trier, and Mainz.

After being elected, the King of the Romans could theoretically claim the title of "Emperor" only after being crowned by the Pope. In many cases, this took several years while the King was held up by other tasks: frequently he first had to resolve conflicts in rebellious northern Italy, or was in quarrel with the Pope himself. Later Emperors dispensed with the papal coronation altogether, being content with the styling Emperor-Elect: the last Emperor to be crowned by the Pope was Charles V in 1530.

The Emperor had to be male and of noble blood. No law required him to be a Catholic, but as the majority of the Electors adhered to this faith, no Protestant was ever elected. Whether and to what degree he had to be German was disputed among the Electors, contemporary experts in constitutional law, and the public. During the Middle Ages, some Kings and Emperors were not of German origin, but since the Renaissance, German heritage was regarded as vital for a candidate in order to be eligible for imperial office.[42]

The Imperial Diet (Reichstag, or Reichsversammlung) was the legislative body of the Holy Roman Empire and theoretically superior to the emperor himself. It was divided into three classes. The first class, the Council of Electors, consisted of the electors, or the princes who could vote for King of the Romans. The second class, the Council of Princes, consisted of the other princes. The Council of Princes was divided into two "benches," one for secular rulers and one for ecclesiastical ones. Higher-ranking princes had individual votes, while lower-ranking princes were grouped into "colleges" by geography. Each college had one vote.

The third class was the Council of Imperial Cities, which was divided into two colleges: Swabia and the Rhine. The Council of Imperial Cities was not fully happy with the others; it could not vote on several matters such as the admission of new territories. The representation of the Free Cities at the Diet had become common since the late Middle Ages. Nevertheless, their participation was formally acknowledged only as late as in 1648 with the Peace of Westphalia ending the Thirty Years' War.

Double-headed eagle with coats of arms of individual states, symbol of the Holy Roman Empire (painting from 1510)

As part of the Imperial Reform, six Imperial Circles were established in 1500; four more were established in 1512. These were regional groupings of most (though not all) of the various states of the Empire for the purposes of defence, imperial taxation, supervision of coining, peace-keeping functions and public security. Each circle had its own parliament, known as a Kreistag ("Circle Diet"), and one or more directors, who coordinated the affairs of the circle. Not all imperial territories were included within the imperial circles, even after 1512; the Lands of the Bohemian Crown were excluded, as were Switzerland, the imperial fiefs in northern Italy, the lands of the Imperial Knights, and certain other small territories like the Lordship of Jever.

The Army of the Holy Roman Empire (German Reichsarmee, Reichsheer or Reichsarmatur; Latin exercitus imperii) was created in 1422, and came to an end even before the Empire as the result of the Napoleonic Wars. It must not be confused with the Imperial Army (Kaiserliche Armee) of the Emperor.

Despite appearances to the contrary, the Army of the Empire did not constitute a permanent standing army which was always at the ready to fight for the Empire. When there was danger, an Army of the Empire was mustered from among the elements constituting it,[43] in order to conduct an imperial military campaign or Reichsheerfahrt. In practice, the imperial troops often had stronger local allegiances than their loyalty to the Emperor.

^The Empire had no official capital, though there was a number of imperial seat cities, which varied throughout history:e.g. Vienna
(Continuous Imperial Residenz City, 1483–1806)Regensburg
(Eternal Diet, 1663–1806)Prague
(1346–1437, 1583–1611)

^Martin Arbage, "Otto I", in Medieval Italy: An Encyclopedia, Volume 2 (Routledge, 2004), p. 810: "Otto can be considered the first ruler of the Holy Roman empire, though that term was not used until the twelfth century."

^The only prince allowed to call himself "king" of a territory in the Empire was the King of Bohemia (after 1556 usually the Emperor himself). Some other princes were kings by virtue of kingdoms they controlled outside of the Empire